Synthesis and intermediates of pyrrolobenzodiazepine derivatives for conjugation

ABSTRACT

A method of synthesing a compound of formula (I) from a compound of formula (III).

The present invention relates to a method of synthesising dimeric PBD compounds bearing a linker for attachment to a cell binding agent.

BACKGROUND

Some pyrrolobenzodiazepines (PBDs) have the ability to recognise and bond to specific sequences of DNA; the preferred sequence is PuGPu. The first PBD antitumour antibiotic, anthramycin, was discovered in 1965 (Leimgruber, et al., J. Am. Chem. Soc., 87, 5793-5795 (1965); Leimgruber, et al., J. Am. Chem. Soc., 87, 5791-5793 (1965)). Since then, a number of naturally occurring PBDs have been reported, and numerous synthetic routes have been developed to a variety of analogues (Thurston, et al., Chem. Rev. 1994, 433-465 (1994); Antonow, D. and Thurston, D. E., Chem. Rev. 2011 111 (4), 2815-2864). Family members include abbeymycin (Hochlowski, et al., J. Antibiotics, 40, 145-148 (1987)), chicamycin (Konishi, et al., J. Antibiotics, 37, 200-206 (1984)), DC-81 (Japanese Patent 58-180 487; Thurston, et al., Chem. Brit., 26, 767-772 (1990); Bose, et al., Tetrahedron, 48, 751-758 (1992)), mazethramycin (Kuminoto, et al., J. Antibiotics, 33, 665-667 (1980)), neothramycins A and B (Takeuchi, et al., J. Antibiotics, 29, 93-96 (1976)), porothramycin (Tsunakawa, et al., J. Antibiotics, 41, 1366-1373 (1988)), prothracarcin (Shimizu, et al, J. Antibiotics, 29, 2492-2503 (1982); Langley and Thurston, J. Org. Chem., 52, 91-97 (1987)), sibanomicin (DC-102)(Hara, et al., J. Antibiotics, 41, 702-704 (1988); Itoh, et al., J. Antibiotics, 41, 1281-1284 (1988)), sibiromycin (Leber, et al., J. Am. Chem. Soc., 110, 2992-2993 (1988)) and tomamycin (Arima, et al., J. Antibiotics, 25, 437-444 (1972)). PBDs are of the general structure:

They differ in the number, type and position of substituents, in both their aromatic A rings and pyrrolo C rings, and in the degree of saturation of the C ring. In the B-ring there is either an imine (N═C), a carbinolamine(NH—CH(OH)), or a carbinolamine methyl ether (NH—CH(OMe)) at the N10-C11 position which is the electrophilic centre responsible for alkylating DNA. All of the known natural products have an (S)-configuration at the chiral C11a position which provides them with a right-handed twist when viewed from the C ring towards the A ring. This gives them the appropriate three-dimensional shape for isohelicity with the minor groove of B-form DNA, leading to a snug fit at the binding site (Kohn, In Antibiotics III. Springer-Verlag, New York, pp. 3-11 (1975); Hurley and Needham-VanDevanter, Acc. Chem. Res., 19, 230-237 (1986)). Their ability to form an adduct in the minor groove, enables them to interfere with DNA processing, hence their use as antitumour agents.

It has been previously disclosed that the biological activity of this molecules can be potentiated by joining two PBD units together through their C8/C′-hydroxyl functionalities via a flexible alkylene linker (Bose, D. S., et al., J. Am. Chem. Soc., 114, 4939-4941 (1992); Thurston, D. E., et al., J. Org. Chem., 61, 8141-8147 (1996)). The PBD dimers are thought to form sequence-selective DNA lesions such as the palindromic 5′-Pu-GATC-Py-3′ interstrand cross-link (Smellie, M., et al., Biochemistry, 42, 8232-8239 (2003); Martin, C., et al., Biochemistry, 44, 4135-4147) which is thought to be mainly responsible for their biological activity. One example of a PBD dimmer, SG2000 (SJG-136):

has recently entered Phase II clinical trials in the oncology area (Gregson, S., et al., J. Med. Chem., 44, 737-748 (2001); Alley, M. C., et al., Cancer Research, 64, 6700-6706 (2004); Hartley, J. A., et al., Cancer Research, 64, 6693-6699 (2004)).

More recently, the present inventors have previously disclosed in WO 2005/085251, dimeric PBD compounds bearing C2 aryl substituents, such as SG2202 (ZC-207):

and in WO2006/111759, bisulphites of such PBD compounds, for example SG2285 (ZC-423):

These compounds have been shown to be highly useful cytotoxic agents (Howard, P. W., et al., Bioorg. Med. Chem. (2009), 19 (22), 6463-6466, doi: 10.1016/j.bmc1.2009.09.012).

WO 2010/043880 discloses unsymmetrical dimeric pyrrolobenzodiazepine (PBD) compound bearing aryl groups in the C2 position of each monomer, where one of these aryl groups bears a substituent designed to provide an anchor for linking the compound to another moiety. WO 2011/130613, discloses the inclusion of these PBD dimer compounds in targeted conjugates.

WO 2011/130616, discloses unsymmetrical dimeric PBD compound bearing an aryl group in the C2 position of one monomer bearing a substituent designed to provide an anchor for linking the compound to another moiety, the other monomer bearing a non-aromatic group in the C2 position. The inclusion of these compounds in targeted conjugates is also disclosed.

Co-pending International application PCT/EP2012/068506, filed 20 Sep. 2012, discloses unsymmetrical dimeric PBD compound bearing an propylyne in the C2 position of one monomer bearing a substituent designed to provide an anchor for linking the compound to another moiety, the other monomer bearing an aromatic or non-aromatic group in the C2 position. The inclusion of these compounds in targeted conjugates is also disclosed.

A further co-pending International application, filed 12 Oct. 2012, and claiming priority from U.S. 61/547,198, discloses unsymmetrical dimeric PBD compound bearing a propylene group in the C2 position of one monomer bearing a substituent designed to provide an anchor for linking the compound to another moiety, the other monomer bearing an aromatic or non-aromatic group in the C2 position. The inclusion of these compounds in targeted conjugates is also disclosed.

The synthesis of the dimeric PBD compounds bearing a linker for attachment to a cell binding agent in these applications is exemplified as proceeding via the drug intended to be released, with the addition of the linking groups to a PBD with no protection at the N10-C11 position.

DISCLOSURE OF THE INVENTION

The present inventors have developed a method of synthesising the dimeric PBD compounds including a linking group as discussed above, which comprises adding part of the linking group to a N10-C11 protected PBD intermediate, and thus eliminating the need to synthesise the drug to be released.

Accordingly, the present invention provides a method of synthesing a compound of formula I:

from a compound of formula III:

wherein:

-   the dotted bond represents an optional double bond between C2′ and     C3′; -   R² is selected from a group of: -   (a) formula IIa:

where A is a C₅₋₇ aryl group, and either:

-   (i) Q¹ is a single bond, and Q² is selected from a single bond and     —Z—(CH₂)_(n)—, where Z is selected from a single bond, O, S and NH     and n is from 1 to 3; or -   (ii) Q¹ is —CH═CH—, and Q² is a single bond; -   (b) formula IIb:

R^(C1), R^(C2) and R^(C3) are independently selected from H and unsubstituted C₁₋₂ alkyl;

-   (c) formula IIc:

L² is selected from a single bond and a group of:

-   (a):

wherein n is 0 to 3;

-   (b)

wherein n is as defined above;

-   (c)

wherein n is as defined above; and

-   (d)

wherein n is as defined above, E is O, S or NR, D is N, CH, or CR, and F is N, CH, or CR;

-   L¹ is:

where X is such that L¹ is a amino-acid residue, a dipeptide residue or a tripeptide residue;

-   Prot is selected from Fmoc (fluorenylmethyloxycarbonyl), Teoc     (2-(trimethylsilyl)ethoxycarbonyl) and Boc (t-butoxycarbonyl); -   when there is a double bond present between C2′ and C3′, R¹² is     selected from: -   (a) C₅₋₁₀ aryl group, optionally substituted by one or more     substituents selected from the group comprising: halo, nitro, cyano,     ether, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; -   (b) C₁₋₅ saturated aliphatic alkyl; -   (c) C₃₋₆ saturated cycloalkyl; -   (d)

wherein each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5;

-   (e)

-    wherein one of R^(25a) and R^(25b) is H and the other is selected     from: phenyl, which phenyl is optionally substituted by a group     selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and -   (f)

-    where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl;     C₂₋₃ alkynyl;     cyclopropyl; phenyl, which phenyl is optionally substituted by a     group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; -   when there is a single bond present between C2′ and C3′, -   R¹² is

-    where R^(26a) and R^(26b) are independently selected from H, F,     C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups     are optionally substituted by a group selected from C₁₋₄ alkyl amido     and C₁₋₄ alkyl ester; or, when one of R^(26a) and R^(26b) is H, the     other is selected from nitrile and a C₁₋₄ alkyl ester; -   R⁶ and R⁹ are independently selected from H, R, OH, OR, SH, SR, NH₂,     NHR, NRR′, nitro, Me₃Sn and halo; -   where R and R′ are independently selected from optionally     substituted C₁₋₁₂ alkyl, C₃₋₂₀ heterocyclyl and C₅₋₂₀ aryl groups; -   R⁷ is selected from H, R, OH, OR, SH, SR, NH₂, NHR, NHRR′, nitro,     Me₃Sn and halo; -   R″ is a C₃₋₁₂ alkylene group, which chain may be interrupted by one     or more heteroatoms, e.g. O, S, NR^(N2) (where R^(N2) is H or C₁₋₄     alkyl), and/or aromatic rings, e.g. benzene or pyridine; -   Y and Y′ are selected from O, S, or NH; -   R^(6′), R^(7′), R^(9′) are selected from the same groups as R⁶, R⁷     and R⁹ respectively.

A second aspect of the present invention provides a compound of formula III.

A third aspect of the present invention provides the use of a compound of formula I in the synthesis of a compound of formula IV and/or V:

wherein the dotted bond, R⁶, R⁷, R⁸, R⁹, Y, R″, Y′, R^(6′), R^(7′), R^(8′), R^(9′) and R¹² are as defined for formula I;

-   R^(2′) is selected from: -   (a) formula IIa′:

where A, Q¹, Q², and L² are as defined for formula I;

-   (b) formula IIb′:

R^(C1), R^(C2) and R^(C3), and L² are as defined for formula I;

-   (c) formula IIc′:

-   L² is as defined for formula I; -   L^(1′) is:

-    where X is as defined for formula I; -   R²″ is selected from: -   (a) formula IIa″:

where A, Q¹, Q², L² and L¹ are as defined for formula I;

-   (b) formula IIb″:

R^(C1), R^(C2) and R^(C3), L² and L¹ are as defined for formula I;

-   (c) formula IIc″:

L² and L¹ are as defined for formula I;

-   G has formula -G¹-G², wherein G¹ selected from: -   (a)

-   where m is from 0 to 6; -   (b)

-    where p is from 0 to 30 and q is 0 or 1; -   and G² is selected from: -   (a)

-   (b)

-   (c)

-    and -   (d)

-    where Hal is Cl, Br or I.

Thus, the third aspect includes the synthesis of a compound of formula IV or V from a compound of III, involving the method of the first aspect of the invention.

The fourth aspect of the present invention provides a method of synthesis of a compound of formula III as defined above, where there is a double bond between C2′ and C3′, from a compound of formula VI:

wherein R⁶, R⁷, R⁸, R⁹, Y, R″, Y′, R^(6′), R^(7′), R^(8′) and R^(9′) are as defined for formula III. This method may proceed via a compound of formula VIIa or VIIb:

wherein R⁶, R⁷, R⁸, R⁹, Y, R″, Y′, R^(6′), R^(7′), R^(8′), R^(9′), R² and R¹² are as defined for formula III.

The fifth aspect of the present invention provides a method of synthesis of a compound of formula III as defined above, where there is no double bond between C2′ and C3′, from a compound of formula VIII:

wherein R⁶, R⁷, R⁸, R⁹, Y, R″, Y′, R^(6′), R^(7′), R^(8′) and R^(9′) are as defined for formula III. This method may proceed via compounds of formula IXa and X:

Or via compounds of formula IXb and X

wherein in all of the compounds R⁶, R⁷, R⁸, R⁹, Y, R″, Y′, R^(6′), R^(7′), R^(8′), R^(9′), R² and R¹² are as defined for formula Ill.

A further aspect provides the reagent coupled to the PBD triflate to form the compound of formula III. This may be of formulae XIa, XIb or XIc:

-   (a)

-   (b)

-   (c)

wherein Q¹, A, Q², R^(C1), R^(C2), R^(C3), L¹, L² and Prot are as defined for formula I; and

-   R^(B) represents boronic acid or a boronate.     Definitions     Substituents

The phrase “optionally substituted” as used herein, pertains to a parent group which may be unsubstituted or which may be substituted.

Unless otherwise specified, the term “substituted” as used herein, pertains to a parent group which bears one or more substituents. The term “substituent” is used herein in the conventional sense and refers to a chemical moiety which is covalently attached to, or if appropriate, fused to, a parent group. A wide variety of substituents are well known, and methods for their formation and introduction into a variety of parent groups are also well known.

Examples of substituents are described in more detail below.

C₁₋₁₂ alkyl: The term “C₁₋₁₂ alkyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 12 carbon atoms, which may be aliphatic or alicyclic, and which may be saturated or unsaturated (e.g. partially unsaturated, fully unsaturated). The term “C₁₋₄ alkyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 4 carbon atoms, which may be aliphatic or alicyclic, and which may be saturated or unsaturated (e.g. partially unsaturated, fully unsaturated). Thus, the term “alkyl” includes the sub-classes alkenyl, alkynyl, cycloalkyl, etc., discussed below.

Examples of saturated alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), propyl (C₃), butyl (C₄), pentyl (C₅), hexyl (C₆) and heptyl (C₇).

Examples of saturated linear alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), n-propyl (C₃), n-butyl (C₄), n-pentyl (amyl) (C₅), n-hexyl (C₆) and n-heptyl (C₇).

Examples of saturated branched alkyl groups include iso-propyl (C₃), iso-butyl (C₄), sec-butyl (C₄), tert-butyl (C₄), iso-pentyl (C₅), and neo-pentyl (C₅).

C₂₋₁₂ Alkenyl: The term “C₂₋₁₂ alkenyl” as used herein, pertains to an alkyl group having one or more carbon-carbon double bonds.

Examples of unsaturated alkenyl groups include, but are not limited to, ethenyl (vinyl, —CH═CH₂), 1-propenyl (—CH═CH—CH₃), 2-propenyl (allyl, —CH—CH═CH₂), isopropenyl (1-methylvinyl, —C(CH₃)═CH₂), butenyl (C₄), pentenyl (C₅), and hexenyl (C₆).

C₂₋₁₂ alkynyl: The term “C₂₋₁₂ alkynyl” as used herein, pertains to an alkyl group having one or more carbon-carbon triple bonds.

Examples of unsaturated alkynyl groups include, but are not limited to, ethynyl (—C≡CH) and 2-propynyl (propargyl, —CH₂—C≡CH).

C₃₋₁₂ cycloalkyl: The term “C₃₋₁₂ cycloalkyl” as used herein, pertains to an alkyl group which is also a cyclyl group; that is, a monovalent moiety obtained by removing a hydrogen atom from an alicyclic ring atom of a cyclic hydrocarbon (carbocyclic) compound, which moiety has from 3 to 7 carbon atoms, including from 3 to 7 ring atoms.

Examples of cycloalkyl groups include, but are not limited to, those derived from:

-   -   saturated monocyclic hydrocarbon compounds:         cyclopropane (C₃), cyclobutane (C₄), cyclopentane (C₅),         cyclohexane (C₆), cycloheptane (C₇), methylcyclopropane (C₄),         dimethylcyclopropane (C₅), methylcyclobutane (C₅),         dimethylcyclobutane (C₆), methylcyclopentane (C₆),         dimethylcyclopentane (C₇) and methylcyclohexane (C₇);     -   unsaturated monocyclic hydrocarbon compounds:         cyclopropene (C₃), cyclobutene (C₄), cyclopentene (C₅),         cyclohexene (C₆), methylcyclopropene (C₄), dimethylcyclopropene         (C₅), methylcyclobutene (C₅), di methylcyclobutene (C₆),         methylcyclopentene (C₆), dimethylcyclopentene (C₇) and         methylcyclohexene (C₇); and     -   saturated polycyclic hydrocarbon compounds:         norcarane (C₇), norpinane (C₇), norbornane (C₇).

C₃₋₂₀ heterocyclyl: The term “C₃₋₂₀ heterocyclyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound, which moiety has from 3 to 20 ring atoms, of which from 1 to 10 are ring heteroatoms. Preferably, each ring has from 3 to 7 ring atoms, of which from 1 to 4 are ring heteroatoms.

In this context, the prefixes (e.g. C₃₋₂₀, C₃₋₇, C₅₋₆, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term “C₅₋₆heterocyclyl”, as used herein, pertains to a heterocyclyl group having 5 or 6 ring atoms.

Examples of monocyclic heterocyclyl groups include, but are not limited to, those derived from:

-   N₁: aziridine (C₃), azetidine (C₄), pyrrolidine (tetrahydropyrrole)     (C₅), pyrroline (e.g., 3-pyrroline, 2,5-dihydropyrrole) (C₅),     2H-pyrrole or 3H-pyrrole (isopyrrole, isoazole) (C₅), piperidine     (C₆), dihydropyridine (C₆), tetrahydropyridine (C₆), azepine (C₇); -   O₁: oxirane (C₃), oxetane (C₄), oxolane (tetrahydrofuran) (C₅),     oxole (dihydrofuran) (C₅), oxane (tetrahydropyran) (C₆),     dihydropyran (C₆), pyran (C₆), oxepin (C₇); -   S₁: thiirane (C₃), thietane (C₄), thiolane (tetrahydrothiophene)     (C₅), thiane (tetrahydrothiopyran) (C₆), thiepane (C₇); -   O₂: dioxolane (C₅), dioxane (C₆), and dioxepane (C₇); -   O₃: trioxane (C₆); -   N₂: imidazolidine (C₅), pyrazolidine (diazolidine) (C₅), imidazoline     (C₅), pyrazoline (dihydropyrazole) (C₅), piperazine (C₆); -   N₁O₁: tetrahydrooxazole (C₅), dihydrooxazole (C₅),     tetrahydroisoxazole (C₅), dihydroisoxazole (C₅), morpholine (C₆),     tetrahydrooxazine (C₆), dihydrooxazine (C₆), oxazine (C₆); -   N₁S₁: thiazoline (C₅), thiazolidine (C₅), thiomorpholine (C₆); -   N₂O₁: oxadiazine (C₆); -   O₁S₁: oxathiole (C₅) and oxathiane (thioxane) (C₆); and, -   N₁O₁S₁: oxathiazine (C₆).

Examples of substituted monocyclic heterocyclyl groups include those derived from saccharides, in cyclic form, for example, furanoses (C₅), such as arabinofuranose, lyxofuranose, ribofuranose, and xylofuranse, and pyranoses (C₆), such as allopyranose, altropyranose, glucopyranose, mannopyranose, gulopyranose, idopyranose, galactopyranose, and talopyranose.

C₅₋₂₀ aryl: The term “C₅₋₂₀ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 3 to 20 ring atoms. The term “C₅₋₇ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 5 to 7 ring atoms and the term “C₅₋₁₀ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 5 to 10 ring atoms. Preferably, each ring has from 5 to 7 ring atoms.

In this context, the prefixes (e.g. C₃₋₂₀, C₅₋₇, C₅₋₆, C₅₋₁₀, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term “C₅₋₆ aryl” as used herein, pertains to an aryl group having 5 or 6 ring atoms.

The ring atoms may be all carbon atoms, as in “carboaryl groups”.

Examples of carboaryl groups include, but are not limited to, those derived from benzene (i.e. phenyl) (C₆), naphthalene (C₁₀), azulene (C₁₀), anthracene (C₁₄), phenanthrene (C₁₄), naphthacene (C₁₉), and pyrene (C₁₆).

Examples of aryl groups which comprise fused rings, at least one of which is an aromatic ring, include, but are not limited to, groups derived from indane (e.g. 2,3-dihydro-1H-indene) (C₉), indene (C₉), isoindene (C₉), tetraline (1,2,3,4-tetrahydronaphthalene (C₁₀), acenaphthene (C₁₂), fluorene (C₁₃), phenalene (C₁₃), acephenanthrene (C₁₅), and aceanthrene (C₁₆).

Alternatively, the ring atoms may include one or more heteroatoms, as in “heteroaryl groups”. Examples of monocyclic heteroaryl groups include, but are not limited to, those derived from:

-   N₁: pyrrole (azole) (C₅), pyridine (azine) (C₆); -   O₁: furan (oxole) (C₅); -   S₁: thiophene (thiole) (C₅); -   N₁O₁: oxazole (C₅), isoxazole (C₅), isoxazine (C₆); -   N₂O₁: oxadiazole (furazan) (C₅); -   N₃O₁: oxatriazole (C₅); -   N₁S₁: thiazole (C₅), isothiazole (C₅); -   N₂: imidazole (1,3-diazole) (C₅), pyrazole (1,2-diazole) (C₅),     pyridazine (1,2-diazine) (C₆), pyrimidine (1,3-diazine) (C₆) (e.g.,     cytosine, thymine, uracil), pyrazine (1,4-diazine) (C₆); -   N₃: triazole (C₅), triazine (C₆); and, -   N₄: tetrazole (C₅).

Examples of heteroaryl which comprise fused rings, include, but are not limited to:

-   -   C₉ (with 2 fused rings) derived from benzofuran (O₁),         isobenzofuran (O₁), indole (N₁), isoindole (N₁), indolizine         (N₁), indoline (N₁), isoindoline (N₁), purine (N₄) (e.g.,         adenine, guanine), benzimidazole (N₂), indazole (N₂),         benzoxazole (N₁O₁), benzisoxazole (N₁O₁), benzodioxole (O₂),         benzofurazan (N₂O₁), benzotriazole (N₃), benzothiofuran (S₁),         benzothiazole (N₁S₁), benzothiadiazole (N₂S);     -   C₁₀ (with 2 fused rings) derived from chromene (O₁), isochromene         (O₁), chroman (O₁), isochroman (O₁), benzodioxan (O₂), quinoline         (N₁), isoquinoline (N₁), quinolizine (N₁), benzoxazine (N₁O₁),         benzodiazine (N₂), pyridopyridine (N₂), quinoxaline (N₂),         quinazoline (N₂), cinnoline (N₂), phthalazine (N₂),         naphthyridine (N₂), pteridine (N₄);     -   C₁₁ (with 2 fused rings) derived from benzodiazepine (N₂);     -   C₁₃ (with 3 fused rings) derived from carbazole (N₁),         dibenzofuran (O₁), dibenzothiophene (S₁), carboline (N₂),         perimidine (N₂), pyridoindole (N₂); and,     -   C₁₄ (with 3 fused rings) derived from acridine (N₁), xanthene         (O₁), thioxanthene (S₁), oxanthrene (O₂), phenoxathiin (O₁S₁),         phenazine (N₂), phenoxazine (N₁O₁), phenothiazine (N₁S₁),         thianthrene (S₂), phenanthridine (N₁), phenanthroline (N₂),         phenazine (N₂).

The above groups, whether alone or part of another substituent, may themselves optionally be substituted with one or more groups selected from themselves and the additional substituents listed below.

-   Halo: —F, —Cl, —Br, and —I. -   Hydroxy: —OH. -   Ether: —OR, wherein R is an ether substituent, for example, a C₁₋₇     alkyl group (also referred to as a C₁₋₇ alkoxy group, discussed     below), a C₃₋₂₀ heterocyclyl group (also referred to as a C₃₋₂₀     heterocyclyloxy group), or a C₅₋₂₀ aryl group (also referred to as a     C₅₋₂₀ aryloxy group), preferably a C₁₋₇alkyl group. -   Alkoxy: —OR, wherein R is an alkyl group, for example, a C₁₋₇ alkyl     group. Examples of C₁₋₇ alkoxy groups include, but are not limited     to, —OMe (methoxy), —OEt (ethoxy), —O(nPr) (n-propoxy), —O(iPr)     (isopropoxy), —O(nBu) (n-butoxy), —O(sBu) (sec-butoxy), —O(iBu)     (isobutoxy), and —O(tBu) (tert-butoxy). -   Acetal: —CH(OR¹)(OR²), wherein R¹ and R² are independently acetal     substituents, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl     group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group, or, in     the case of a “cyclic” acetal group, R¹ and R², taken together with     the two oxygen atoms to which they are attached, and the carbon     atoms to which they are attached, form a heterocyclic ring having     from 4 to 8 ring atoms. Examples of acetal groups include, but are     not limited to, —CH(OMe)₂, —CH(OEt)₂, and —CH(OMe)(OEt). -   Hemiacetal: —CH(OH)(OR¹), wherein R¹ is a hemiacetal substituent,     for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a     C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of     hemiacetal groups include, but are not limited to, —CH(OH)(OMe) and     —CH(OH)(OEt). -   Ketal: —CR(OR¹)(OR²), where R¹ and R² are as defined for acetals,     and R is a ketal substituent other than hydrogen, for example, a     C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group,     preferably a C₁₋₇ alkyl group. Examples ketal groups include, but     are not limited to, —C(Me)(OMe)₂, —C(Me)(OEt)₂, —C(Me)(OMe)(OEt),     —C(Et)(OMe)₂, —C(Et)(OEt)₂, and —C(Et)(OMe)(OEt). -   Hemiketal: —CR(OH)(OR¹), where R¹ is as defined for hemiacetals, and     R is a hemiketal substituent other than hydrogen, for example, a     C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group,     preferably a C₁₋₇ alkyl group. Examples of hemiacetal groups     include, but are not limited to, —C(Me)(OH)(OMe), —C(Et)(OH)(OMe),     —C(Me)(OH)(OEt), and —C(Et)(OH)(OEt). -   Oxo (keto, -one): ═O. -   Thione (thioketone): ═S. -   Imino (imine): ═NR, wherein R is an imino substituent, for example,     hydrogen, C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀     aryl group, preferably hydrogen or a C₁₋₇ alkyl group. Examples of     ester groups include, but are not limited to, ═NH, =NMe, =NEt, and     ═NPh. -   Formyl (carbaldehyde, carboxaldehyde): —C(═O)H. -   Acyl (keto): —C(═O)R, wherein R is an acyl substituent, for example,     a C₁₋₇ alkyl group (also referred to as C₁₋₇ alkylacyl or C₁₋₇     alkanoyl), a C₃₋₂₀ heterocyclyl group (also referred to as C₃₋₂₀     heterocyclylacyl), or a C₅₋₂₀ aryl group (also referred to as C₅₋₂₀     arylacyl), preferably a C₁₋₇ alkyl group. Examples of acyl groups     include, but are not limited to, —C(═O)CH₃ (acetyl), —C(═O)CH₂CH₃     (propionyl), —C(═O)C(CH₃)₃ (t-butyryl), and —C(═O)Ph (benzoyl,     phenone). -   Carboxy (carboxylic acid): —C(═O)OH. -   Thiocarboxy (thiocarboxylic acid): —C(═S)SH. -   Thiolocarboxy (thiolocarboxylic acid): —C(═O)SH. -   Thionocarboxy (thionocarboxylic acid): —C(═S)OH. -   Imidic acid: —C(═NH)OH. -   Hydroxamic acid: —C(═NOH)OH. -   Ester (carboxylate, carboxylic acid ester, oxycarbonyl): —C(═O)OR,     wherein R is an ester substituent, for example, a C₁₋₇ alkyl group,     a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇     alkyl group. Examples of ester groups include, but are not limited     to, —C(═O)OCH₃, —C(═O)OCH₂CH₃, —C(═O)OC(CH₃)₃, and —C(═O)OPh. -   Acyloxy (reverse ester): —OC(═O)R, wherein R is an acyloxy     substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl     group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group.     Examples of acyloxy groups include, but are not limited to,     —OC(═O)CH₃ (acetoxy), —OC(═O)CH₂CH₃, —OC(═O)C(CH₃)₃, —OC(═O)Ph, and     —OC(═O)CH₂Ph. -   Oxycarboyloxy: —OC(═O)OR, wherein R is an ester substituent, for     example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀     aryl group, preferably a C₁₋₇ alkyl group. Examples of ester groups     include, but are not limited to, —OC(═O)OCH₃, —OC(═O)OCH₂CH₃,     —OC(═O)OC(CH₃)₃, and —OC(═O)OPh. -   Amino: —NR¹R², wherein R¹ and R² are independently amino     substituents, for example, hydrogen, a C₁₋₇ alkyl group (also     referred to as C₁₋₇ alkylamino or di-C₁₋₇ alkylamino), a C₃₋₂₀     heterocyclyl group, or a C₅₋₂₀ aryl group, preferably H or a C₁₋₇     alkyl group, or, in the case of a “cyclic” amino group, R¹ and R²,     taken together with the nitrogen atom to which they are attached,     form a heterocyclic ring having from 4 to 8 ring atoms. Amino groups     may be primary (—NH₂), secondary (—NHR¹), or tertiary (—NHR¹R²), and     in cationic form, may be quaternary (—⁺NR¹R²R³). Examples of amino     groups include, but are not limited to, —NH₂, —NHCH₃, —NHC(CH₃)₂,     —N(CH₃)₂, —N(CH₂CH₃)₂, and —NHPh. Examples of cyclic amino groups     include, but are not limited to, aziridino, azetidino, pyrrolidino,     piperidino, piperazino, morpholino, and thiomorpholino. -   Amido (carbamoyl, carbamyl, aminocarbonyl, carboxamide):     —C(═O)NR¹R², wherein R¹ and R² are independently amino substituents,     as defined for amino groups. Examples of amido groups include, but     are not limited to, —C(═O)NH₂, —C(═O)NHCH₃, —C(═O)N(CH₃)₂,     —C(═O)NHCH₂CH₃, and —C(═O)N(CH₂CH₃)₂, as well as amido groups in     which R¹ and R², together with the nitrogen atom to which they are     attached, form a heterocyclic structure as in, for example,     piperidinocarbonyl, morpholinocarbonyl, thiomorpholinocarbonyl, and     piperazinocarbonyl. -   Thioamido (thiocarbamyl): —C(═S)NR¹R², wherein R¹ and R² are     independently amino substituents, as defined for amino groups.     Examples of amido groups include, but are not limited to, —C(═S)NH₂,     —C(═S)NHCH₃, —C(═S)N(CH₃)₂, and —C(═S)NHCH₂CH₃. -   Acylamido (acylamino): —NR¹C(═O)R², wherein R¹ is an amide     substituent, for example, hydrogen, a C₁₋₇alkyl group, a C₃₋₂₀     heterocyclyl group, or a C₅₋₂₀ aryl group, preferably hydrogen or a     C₁₋₇ alkyl group, and R² is an acyl substituent, for example, a C₁₋₇     alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀aryl group,     preferably hydrogen or a C₁₋₇alkyl group. Examples of acylamide     groups include, but are not limited to, —NHC(═O)CH₃, —NHC(═O)CH₂CH₃,     and —NHC(═O)Ph. R¹ and R² may together form a cyclic structure, as     in, for example, succinimidyl, maleimidyl, and phthalimidyl:

Aminocarbonyloxy: —OC(═O)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of aminocarbonyloxy groups include, but are not limited to, —OC(═O)NH₂, —OC(═O)NHMe, —OC(═O)NMe₂, and —OC(═O)NEt₂.

-   Ureido: —N(R¹)CONR²R³ wherein R² and R³ are independently amino     substituents, as defined for amino groups, and R¹ is a ureido     substituent, for example, hydrogen, a C₁₋₇alkyl group, a C₃₋₂₀     heterocyclyl group, or a C₅₋₂₀ aryl group, preferably hydrogen or a     C₁₋₇alkyl group. Examples of ureido groups include, but are not     limited to, —NHCONH₂, —NHCONHMe, —NHCONHEt, —NHCONMe₂, —NHCONEt₂,     —NMeCONH₂, —NMeCONHMe, —NMeCONHEt, —NMeCONMe₂, and —NMeCONEt₂. -   Guanidino: —NH—C(═NH)NH₂. -   Tetrazolyl: a five membered aromatic ring having four nitrogen atoms     and one carbon atom,

Imino: ═NR, wherein R is an imino substituent, for example, for example, hydrogen, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably H or a C₁₋₇alkyl group. Examples of imino groups include, but are not limited to, ═NH, =NMe, and =NEt.

-   Amidine (amidino): —C(═NR)NR₂, wherein each R is an amidine     substituent, for example, hydrogen, a C₁₋₇ alkyl group, a C₃₋₂₀     heterocyclyl group, or a C₅₋₂₀ aryl group, preferably H or a C₁₋₇     alkyl group. Examples of amidine groups include, but are not limited     to, —C(═NH)NH₂, —C(═NH)NMe₂, and —C(═NMe)NMe₂. -   Nitro: —NO₂. -   Nitroso: —NO. -   Azido: —N₃. -   Cyano (nitrile, carbonitrile): —CN. -   Isocyano: —NC. -   Cyanato: —OCN. -   Isocyanato: —NCO. -   Thiocyano (thiocyanato): —SCN. -   Isothiocyano (isothiocyanato): —NCS. -   Sulfhydryl (thiol, mercapto): —SH. -   Thioether (sulfide): —SR, wherein R is a thioether substituent, for     example, a C₁₋₇ alkyl group (also referred to as a C₁₋₇alkylthio     group), a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group,     preferably a C₁₋₇ alkyl group. Examples of C₁₋₇ alkylthio groups     include, but are not limited to, —SCH₃ and —SCH₂CH₃. -   Disulfide: —SS—R, wherein R is a disulfide substituent, for example,     a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl     group, preferably a C₁₋₇ alkyl group (also referred to herein as     C₁₋₇ alkyl disulfide). Examples of C₁₋₇ alkyl disulfide groups     include, but are not limited to, —SSCH₃ and —SSCH₂CH₃. -   Sulfine (sulfinyl, sulfoxide): —S(═O)R, wherein R is a sulfine     substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl     group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group.     Examples of sulfine groups include, but are not limited to,     —S(═O)CH₃ and —S(═O)CH₂CH₃. -   Sulfone (sulfonyl): —S(═O)₂R, wherein R is a sulfone substituent,     for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a     C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group, including, for     example, a fluorinated or perfluorinated C₁₋₇ alkyl group. Examples     of sulfone groups include, but are not limited to, —S(═O)₂CH₃     (methanesulfonyl, mesyl), —S(═O)₂CF₃ (triflyl), —S(═O)₂CH₂CH₃     (esyl), —S(═O)₂C₄F₉ (nonaflyl), —S(═O)₂CH₂CF₃ (tresyl),     —S(═O)₂CH₂CH₂NH₂ (tauryl), —S(═O)₂Ph (phenylsulfonyl, besyl),     4-methylphenylsulfonyl (tosyl), 4-chlorophenylsulfonyl (closyl),     4-bromophenylsulfonyl (brosyl), 4-nitrophenyl (nosyl),     2-naphthalenesulfonate (napsyl), and     5-dimethylamino-naphthalen-1-ylsulfonate (dansyl). -   Sulfinic acid (sulfino): —S(═O)OH, —SO₂H. -   Sulfonic acid (sulfo): —S(═O)₂OH, —SO₃H. -   Sulfinate (sulfinic acid ester): —S(═O)OR; wherein R is a sulfinate     substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl     group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group.     Examples of sulfinate groups include, but are not limited to,     —S(═O)OCH₃ (methoxysulfinyl; methyl sulfinate) and —S(═O)OCH₂CH₃     (ethoxysulfinyl; ethyl sulfinate). -   Sulfonate (sulfonic acid ester): —S(═O)₂OR, wherein R is a sulfonate     substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl     group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group.     Examples of sulfonate groups include, but are not limited to,     —S(═O)₂OCH₃ (methoxysulfonyl; methyl sulfonate) and —S(═O)₂OCH₂CH₃     (ethoxysulfonyl; ethyl sulfonate). -   Sulfinyloxy: —OS(═O)R, wherein R is a sulfinyloxy substituent, for     example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀     aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfinyloxy     groups include, but are not limited to, —OS(═O)CH₃ and     —OS(═O)CH₂CH₃. -   Sulfonyloxy: —OS(═O)₂R, wherein R is a sulfonyloxy substituent, for     example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀     aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfonyloxy     groups include, but are not limited to, —OS(═O)₂CH₃ (mesylate) and     —OS(═O)₂CH₂CH₃ (esylate). -   Sulfate: —OS(═O)₂OR; wherein R is a sulfate substituent, for     example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀     aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfate     groups include, but are not limited to, —OS(═O)₂OCH₃ and     —SO(═O)₂OCH₂CH₃. -   Sulfamyl (sulfamoyl; sulfinic acid amide; sulfinamide): —S(═O)NR¹R²,     wherein R¹ and R² are independently amino substituents, as defined     for amino groups. Examples of sulfamyl groups include, but are not     limited to, —S(═O)NH₂, —S(═O)NH(CH₃), —S(═O)N(CH₃)₂,     —S(═O)NH(CH₂CH₃), —S(═O)N(CH₂CH₃)₂, and —S(═O)NHPh. -   Sulfonamido (sulfinamoyl; sulfonic acid amide; sulfonamide):     —S(═O)₂NR¹R², wherein R¹ and R² are independently amino     substituents, as defined for amino groups. Examples of sulfonamido     groups include, but are not limited to, —S(═O)₂NH₂, —S(═O)₂NH(CH₃),     —S(═O)₂N(CH₃)₂, —S(═O)₂NH(CH₂CH₃), —S(═O)₂N(CH₂CH₃)₂, and     —S(═O)₂NHPh. -   Sulfamino: —NR¹S(═O)₂OH, wherein R¹ is an amino substituent, as     defined for amino groups. Examples of sulfamino groups include, but     are not limited to, —NHS(═O)₂OH and —N(CH₃)S(═O)₂OH. -   Sulfonamino: —NR¹S(═O)₂R, wherein R¹ is an amino substituent, as     defined for amino groups, and R is a sulfonamino substituent, for     example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀     aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfonamino     groups include, but are not limited to, —NHS(═O)₂CH₃ and     —N(CH₃)S(═O)₂C₆H₅. -   Sulfinamino: —NR¹S(═O)R, wherein R¹ is an amino substituent, as     defined for amino groups, and R is a sulfinamino substituent, for     example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀     aryl group, preferably a C₁₋₇ alkyl group. Examples of sulfinamino     groups include, but are not limited to, —NHS(═O)CH₃ and     —N(CH₃)S(═O)C₆H₅. -   Phosphino (phosphine): —PR₂, wherein R is a phosphino substituent,     for example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or     a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀     aryl group. Examples of phosphino groups include, but are not     limited to, —PH₂, —P(CH₃)₂, —P(CH₂CH₃)₂, —P(t-Bu)₂, and —P(Ph)₂. -   Phospho: —P(═O)₂. -   Phosphinyl (phosphine oxide): —P(═O)R₂, wherein R is a phosphinyl     substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl     group, or a C₅₋₂₀ aryl group, preferably a C₁₋₇ alkyl group or a     C₅₋₂₀ aryl group. Examples of phosphinyl groups include, but are not     limited to, —P(═O)(CH₃)₂, —P(═O)(CH₂CH₃)₂, —P(═O)(t-Bu)₂, and     —P(═O)(Ph)₂. -   Phosphonic acid (phosphono): —P(═O)(OH)₂. -   Phosphonate (phosphono ester): —P(═O)(OR)₂, where R is a phosphonate     substituent, for example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀     heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇     alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphonate groups     include, but are not limited to, —P(═O)(OCH₃)₂, —P(═O)(OCH₂CH₃)₂,     —P(═O)(O-t-Bu)₂, and —P(═O)(OPh)₂. -   Phosphoric acid (phosphonooxy): —OP(═O)(OH)₂. -   Phosphate (phosphonooxy ester): —OP(═O)(OR)₂, where R is a phosphate     substituent, for example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀     heterocyclyl group, or a C₅₋₂₀ aryl group, preferably —H, a C₁₋₇     alkyl group, or a C₅₋₂₀ aryl group. Examples of phosphate groups     include, but are not limited to, —OP(═O)(OCH₃)₂, —OP(═O)(OCH₂CH₃)₂,     —OP(═O)(O-t-Bu)₂, and —OP(═O)(OPh)₂. -   Phosphorous acid: —OP(OH)₂. -   Phosphite: —OP(OR)₂, where R is a phosphite substituent, for     example, —H, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a     C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl     group. Examples of phosphite groups include, but are not limited to,     —OP(OCH₃)₂, —OP(OCH₂CH₃)₂, —OP(O-t-Bu)₂, and —OP(OPh)₂. -   Phosphoramidite: —OP(OR¹)—NR² ₂, where R¹ and R² are phosphoramidite     substituents, for example, —H, a (optionally substituted) C₁₋₇ alkyl     group, a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably     —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl group. Examples of     phosphoramidite groups include, but are not limited to,     —OP(OCH₂CH₃)—N(CH₃)₂, —OP(OCH₂CH₃)—N(i-Pr)₂, and     —OP(OCH₂CH₂CN)—N(i-Pr)₂. -   Phosphoramidate: —OP(═O)(OR¹)—NR² ₂, where R¹ and R² are     phosphoramidate substituents, for example, —H, a (optionally     substituted) C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a     C₅₋₂₀ aryl group, preferably —H, a C₁₋₇ alkyl group, or a C₅₋₂₀ aryl     group. Examples of phosphoramidate groups include, but are not     limited to, —OP(═O)(OCH₂CH₃)—N(CH₃)₂, —OP(═O)(OCH₂CH₃)—N(i-Pr)₂, and     —OP(═O)(OCH₂CH₂CN)—N(i-Pr)₂.     Alkylene

C₃₋₁₂ alkylene: The term “C₃₋₁₂ alkylene”, as used herein, pertains to a bidentate moiety obtained by removing two hydrogen atoms, either both from the same carbon atom, or one from each of two different carbon atoms, of a hydrocarbon compound having from 3 to 12 carbon atoms (unless otherwise specified), which may be aliphatic or alicyclic, and which may be saturated, partially unsaturated, or fully unsaturated. Thus, the term “alkylene” includes the sub-classes alkenylene, alkynylene, cycloalkylene, etc., discussed below.

Examples of linear saturated C₃₋₁₂ alkylene groups include, but are not limited to, —(CH₂)_(n)— where n is an integer from 3 to 12, for example, —CH₂CH₂CH₂— (propylene), —CH₂CH₂CH₂CH₂— (butylene), —CH₂CH₂CH₂CH₂CH₂— (pentylene) and —CH₂CH₂CH₂CH-₂CH₂CH₂CH₂— (heptylene).

Examples of branched saturated C₃₋₁₂ alkylene groups include, but are not limited to, —CH(CH₃)CH₂—, —CH(CH₃)CH₂CH₂—, —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂—, —CH₂CH(CH₃)CH₂CH₂—, —CH(CH₂CH₃)—, —CH(CH₂CH₃)CH₂—, and —CH₂CH(CH₂CH₃)CH₂—.

Examples of linear partially unsaturated C₃₋₁₂ alkylene groups (C₃₋₁₂ alkenylene, and alkynylene groups) include, but are not limited to, —CH═CH—CH₂—, —CH₂—CH═CH₂—, —CH═CH—CH₂—CH₂—, —CH═CH—CH₂—CH₂—CH₂—, —CH═CH—CH═CH—, —CH═CH—CH═CH—CH₂—, —CH═CH—CH═CH—CH₂—CH₂—, —CH═CH—CH₂—CH═CH—, —CH═CH—CH₂—CH₂—CH═CH—, and —CH₂—C≡C—CH₂—.

Examples of branched partially unsaturated C₃₋₁₂ alkylene groups (C₃₋₁₂ alkenylene and alkynylene groups) include, but are not limited to, —C(CH₃)═CH—, —C(CH₃)═CH—CH₂—, —CH═CH—CH(CH₃)— and —C≡C—CH(CH₃)—.

Examples of alicyclic saturated C₃₋₁₂ alkylene groups (C₃₋₁₂ cycloalkylenes) include, but are not limited to, cyclopentylene (e.g. cyclopent-1,3-ylene), and cyclohexylene (e.g. cyclohex-1,4-ylene).

Examples of alicyclic partially unsaturated C₃₋₁₂ alkylene groups (C₃₋₁₂ cycloalkylenes) include, but are not limited to, cyclopentenylene (e.g. 4-cyclopenten-1,3-ylene), cyclohexenylene (e.g. 2-cyclohexen-1,4-ylene; 3-cyclohexen-1,2-ylene; 2,5-cyclohexadien-1,4-ylene).

Further Preferences

The following preferences may apply to all aspects of the invention as described above, or may relate to a single aspect. The preferences may be combined together in any combination.

In some embodiments, R^(6′), R^(7′), R^(9′) and Y′ are preferably the same as R⁶, R⁷, R⁹ and Y respectively.

Dimer Link

Y and Y′ are preferably O.

R″ is preferably a C₃₋₇ alkylene group with no substituents. More preferably R″ is a C₃, C₅ or C₇ alkylene. Most preferably, R″ is a C₃ or C₅ alkylene.

R⁶ to R⁹

R⁹ is preferably H.

R⁶ is preferably selected from H, OH, OR, SH, NH₂, nitro and halo, and is more preferably H or halo, and most preferably is H.

R⁷ is preferably selected from H, OH, OR, SH, SR, NH₂, NHR, NRR′, and halo, and more preferably independently selected from H, OH and OR, where R is preferably selected from optionally substituted C₁₋₇ alkyl, C₃₋₁₀ heterocyclyl and C₅₋₁₀ aryl groups. R may be more preferably a C₁₋₄ alkyl group, which may or may not be substituted. A substituent of interest is a C₅₋₆ aryl group (e.g. phenyl). Particularly preferred substituents at the 7-positions are OMe and OCH₂Ph. Other substituents of particular interest are dimethylamino (i.e. —NMe₂); —(OC₂H₄)_(q)OMe, where q is from 0 to 2; nitrogen-containing C₆ heterocyclyls, including morpholino, piperidinyl and N-methyl-piperazinyl.

These preferences apply to R^(9′), R^(6′) and R^(7′) respectively.

R¹²

R¹² is selected from:

-   (a) C₅₋₁₀ aryl group, optionally substituted by one or more     substituents selected from the group comprising: halo, nitro, cyano,     ether, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; -   (b) C₁₋₅ saturated aliphatic alkyl; -   (c) C₃₋₆ saturated cycloalkyl; -   (d)

-    wherein each of R²¹, R²² and R²³ are independently selected from H,     C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl,     where the total number of carbon atoms in the R¹² group is no more     than 5; -   (e)

-    wherein one of R^(25a) and R^(25b) is H and the other is selected     from: phenyl, which phenyl is optionally substituted by a group     selected from halo methyl, methoxy; pyridyl; and thiophenyl; and -   (f)

-    where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl;     C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally     substituted by a group selected from halo methyl, methoxy; pyridyl;     and thiophenyl.

When R¹² is a C₅₋₁₀ aryl group, it may be a C₅₋₇ aryl group. A C₅₋₇ aryl group may be a phenyl group or a C₅₋₇ heteroaryl group, for example furanyl, thiophenyl and pyridyl. In some embodiments, R¹² is preferably phenyl. In other embodiments, R¹² is preferably thiophenyl, for example, thiophen-2-yl and thiophen-3-yl.

When R¹² is a C₅₋₁₀ aryl group, it may be a C₈₋₁₀ aryl, for example a quinolinyl or isoquinolinyl group. The quinolinyl or isoquinolinyl group may be bound to the PBD core through any available ring position. For example, the quinolinyl may be quinolin-2-yl, quinolin-3-yl, quinolin-4yl, quinolin-5-yl, quinolin-6-yl, quinolin-7-yl and quinolin-8-yl. Of these quinolin-3-yl and quinolin-6-yl may be preferred. The isoquinolinyl may be isoquinolin-1-yl, isoquinolin-3-yl, isoquinolin-4yl, isoquinolin-5-yl, isoquinolin-6-yl, isoquinolin-7-yl and isoquinolin-8-yl. Of these isoquinolin-3-yl and isoquinolin-6-yl may be preferred.

When R¹² is a C₅₋₁₀ aryl group, it may bear any number of substituent groups. It preferably bears from 1 to 3 substituent groups, with 1 and 2 being more preferred, and singly substituted groups being most preferred. The substituents may be any position.

Where R¹² is C₅₋₇ aryl group, a single substituent is preferably on a ring atom that is not adjacent the bond to the remainder of the compound, i.e. it is preferably β or γ to the bond to the remainder of the compound. Therefore, where the C₅₋₇ aryl group is phenyl, the substituent is preferably in the meta- or para-positions, and more preferably is in the para-position.

Where R¹² is a C₈₋₁₀ aryl group, for example quinolinyl or isoquinolinyl, it may bear any number of substituents at any position of the quinoline or isoquinoline rings. In some embodiments, it bears one, two or three substituents, and these may be on either the proximal and distal rings or both (if more than one substituent).

R¹² Substituents, when R¹² is a C₅₋₁₀ Aryl Group

If a substituent on R¹² when R¹² is a C₆₋₁₀ aryl group is halo, it is preferably F or Cl, more preferably F.

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is ether, it may in some embodiments be an alkoxy group, for example, a C₁₋₇ alkoxy group (e.g. methoxy, ethoxy) or it may in some embodiments be a C₅₋₇ aryloxy group (e.g phenoxy, pyridyloxy, furanyloxy). The alkoxy group may itself be further substituted, for example by an amino group (e.g. dimethylamino).

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is C₁₋₇ alkyl, it may preferably be a C₁₋₄ alkyl group (e.g. methyl, ethyl, propyl, butyl).

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is C₃₋₇ heterocyclyl, it may in some embodiments be C₆ nitrogen containing heterocyclyl group, e.g. morpholino, thiomorpholino, piperidinyl, piperazinyl. These groups may be bound to the rest of the PBD moiety via the nitrogen atom. These groups may be further substituted, for example, by C₁₋₄ alkyl groups. If the C₆ nitrogen containing heterocyclyl group is piperazinyl, the said further substituent may be on the second nitrogen ring atom.

If a substituent on R¹² when R¹² is a C₅₋₁₀ aryl group is bis-oxy-C₁₋₃ alkylene, this is preferably bis-oxy-methylene or bis-oxy-ethylene.

Particularly preferred substituents when R¹² is a C₅₋₁₀ aryl group include methoxy, ethoxy, fluoro, chloro, cyano, bis-oxy-methylene, methyl-piperazinyl, morpholino and methylthiophenyl. Another particularly preferred substituent for R¹² is dimethylaminopropyloxy.

Particularly preferred substituted R¹² groups when R¹² is a C₅₋₁₀ aryl group include, but are not limited to, 4-methoxy-phenyl, 3-methoxyphenyl, 4-methylphenyl, 4-ethoxy-phenyl, 3-ethoxy-phenyl, 4-fluoro-phenyl, 4-chloro-phenyl, 3,4-bisoxymethylene-phenyl, 4-methylthiophenyl, 4-cyanophenyl, 4-phenoxyphenyl, quinolin-3-yl and quinolin-6-yl, isoquinolin-3-yl and isoquinolin-6-yl, 2-thienyl, 2-furanyl, methoxynaphthyl, and naphthyl. Another possible substituted R¹² group is 4-nitrophenyl.

When R¹² is C₁₋₅ saturated aliphatic alkyl, it may be methyl, ethyl, propyl, butyl or pentyl. In some embodiments, it may be methyl, ethyl or propyl (n-pentyl or isopropyl). In some of these embodiments, it may be methyl. In other embodiments, it may be butyl or pentyl, which may be linear or branched.

When R¹² is C₃₋₆ saturated cycloalkyl, it may be cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl. In some embodiments, it may be cyclopropyl.

When R¹² is

each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5. In some embodiments, the total number of carbon atoms in the R¹² group is no more than 4 or no more than 3.

In some embodiments, one of R²¹, R²² and R²³ is H, with the other two groups being selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl.

In other embodiments, two of R²¹, R²² and R²³ are H, with the other group being selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl.

In some embodiments, the groups that are not H are selected from methyl and ethyl. In some of these embodiments, the groups that are not H are methyl.

In some embodiments, R²¹ is H.

In some embodiments, R²² is H.

In some embodiments, R²³ is H.

In some embodiments, R²¹ and R²² are H.

In some embodiments, R²¹ and R²³ are H.

In some embodiments, R²² and R²³ are H.

An R¹² group of particular interest is:

When R¹² is

one of R^(25a) and R^(25b) is H and the other is selected from:

-   -   phenyl, which phenyl is optionally substituted by a group         selected from halo, methyl, methoxy; pyridyl; and thiophenyl. In         some embodiments, the group which is not H is optionally         substituted phenyl. If the phenyl optional substituent is halo,         it is preferably fluoro. In some embodiment, the phenyl group is         unsubstituted.

When R¹² is

R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo methyl, methoxy; pyridyl; and thiophenyl. If the phenyl optional substituent is halo, it is preferably fluoro. In some embodiment, the phenyl group is unsubstituted.

In some embodiments, R²⁴ is selected from H, methyl, ethyl, ethenyl and ethynyl. In some of these embodiments, R²⁴ is selected from H and methyl.

IIa

A in R² may be phenyl group or a C₅₋₇ heteroaryl group, for example furanyl, thiophenyl and pyridyl. In some embodiments, A is preferably phenyl.

Q² may be on any of the available ring atoms of the C₅₋₇ aryl group, but is preferably on a ring atom that is not adjacent the bond to the remainder of the compound, i.e. it is preferably β or γ to the bond to the remainder of the compound. Therefore, where the C₅₋₇ aryl group (A) is phenyl, the substituent (Q²-X) is preferably in the meta- or para-positions, and more preferably is in the para-position.

In some embodiments, Q¹ is a single bond. In these embodiments, Q² is selected from a single bond and —Z—(CH₂)_(n)—, where Z is selected from a single bond, O, S and NH and is from 1 to 3. In some of these embodiments, Q² is a single bond. In other embodiments, Q² is —Z—(CH₂)_(n)—. In these embodiments, Z may be O or S and n may be 1 or n may be 2. In other of these embodiments, Z may be a single bond and n may be 1.

In other embodiments, Q¹ is —CH═CH—.

In some embodiments, R² may be -A-CH₂—NH-L²-L¹-Prot and -A-NH-L²-L¹-Prot.

IIb

R^(C1), R^(C2) and R^(C3) are independently selected from H and unsubstituted C₁₋₂ alkyl. In some preferred embodiments, R^(C1), R^(C2) and R^(C3) are all H. In other embodiments, R^(C1), R^(C2) and R^(C3) are all methyl. In certain embodiments, R^(C1), R^(C2) and R^(C3) are independently selected from H and methyl.

L²

In some embodiments, L² is a single bond.

In some embodiments, L² is:

wherein n is 0 to 3. In these embodiments, n can be 0, 1, 2 or 3. n=0 and n=1 may be preferred.

In some embodiments, L² is:

wherein n is 0 to 3. In these embodiments, n can be 0, 1, 2 or 3. n=0 and n=1 may be preferred.

In some embodiments, L² is:

wherein n is 0 to 3. In these embodiments, n can be 0, 1, 2 or 3. n=0 and n=1 may be preferred.

In some embodiments, L² is:

wherein n is 0 to 3. In these embodiments, n can be 0, 1, 2 or 3. n=0 and n=1 may be preferred. In one of these embodiments, D is N. In other of these embodiments, D is CH. In one of these embodiments, E is O or S. In one these embodiments, F is CH. L¹/L^(1′)

In one embodiment, L¹/L^(1′) are an amino acid residue. The amino acid may a natural amino acids or a non-natural amino acid.

In one embodiment, L¹ is selected from: Phe, Lys, Val, Ala, Cit, Leu, Ile, Arg, and Trp, where Cit is citrulline.

In one embodiment, L¹/L^(1′) comprises a dipeptide residue. The amino acids in the dipeptide may be any combination of natural amino acids and non-natural amino acids. In some embodiments, the dipeptide comprises natural amino acids. Where the linker is a cathepsin labile linker, the dipeptide is the site of action for cathepsin-mediated cleavage. The dipeptide then is a recognition site for cathepsin.

In one embodiment, L¹ is selected from:

-   -   ^(Prot)-Phe-Lys-^(L2),     -   ^(Prot)-Val-Ala-^(L2),     -   ^(Prot)-Val-Lys-^(L2),     -   ^(Prot)-Ala-Lys-^(L2),     -   ^(Prot)-Val-Cit-^(L2),     -   ^(Prot)-Phe-Cit-^(L2),     -   ^(Prot)-Leu-Cit-^(L2),     -   ^(Prot)-Ile-Cit-^(L2),     -   ^(Prot)-Phe-Arg-^(L2), and     -   ^(Prot)-Trp-Cit-^(L2);         where Cit is citrulline.

Preferably, L¹ is selected from:

-   -   ^(Prot)-Phe-Lys-^(L2),     -   ^(Prot)-Val-Ala-^(L2),     -   ^(Prot)-Val-Lys-^(L2),     -   ^(Prot)-Ala-Lys-^(L2), and     -   ^(Prot)-Val-Cit-^(L2).

Most preferably, L¹ is selected from ^(Prot)-Phe-Lys-^(L2), ^(Prot)-Val-Cit-^(L2) or ^(Prot)-Val-Ala-^(L2).

Other dipeptide combinations of interest include:

-   -   ^(Prot)-Gly-Gly-^(L2),     -   ^(Prot)-Pro-Pro-^(L2), and     -   ^(Prot)-Val-Glu-^(L2).

Other dipeptide combinations may be used, including those described by Dubowchik et al., Bioconjugate Chemistry, 2002, 13, 855-869, which is incorporated herein by reference.

In some embodiments, L¹/L^(1′) are tripeptide residue. The amino acids in the tripeptide may be any combination of natural amino acids and non-natural amino acids. In some embodiments, the tripeptide comprises natural amino acids. Where the linker is a cathepsin labile linker, the tripeptide is the site of action for cathepsin-mediated cleavage. The tripeptide then is a recognition site for cathepsin.

In one embodiment, the amino acid side chain is chemically protected, where appropriate. The side chain protecting group may be a group as discussed below. Protected amino acid sequences are cleavable by enzymes. For example, a dipeptide sequence comprising a Boc side chain-protected Lys residue is cleavable by cathepsin.

Protecting groups for the side chains of amino acids are well known in the art and are described in the Novabiochem Catalog. Additional protecting group strategies are set out in Protective groups in Organic Synthesis, Greene and Wuts.

Possible side chain protecting groups are shown below for those amino acids having reactive side chain functionality:

-   -   Arg: Z, Mtr, Tos;     -   Asn: Trt, Xan;     -   Asp: Bzl, t-Bu;     -   Cys: Acm, Bzl, Bzl-OMe, Bzl-Me, Trt;     -   Glu: Bzl, t-Bu;     -   Gln: Trt, Xan;     -   His: Boc, Dnp, Tos, Trt;     -   Lys: Boc, Z-Cl, Fmoc, Z;     -   Ser: Bzl, TBDMS, TBDPS;     -   Thr: Bz;     -   Trp: Boc;     -   Tyr: Bzl, Z, Z-Br.         Prot

Prot is selected from Fmoc (fluorenylmethyloxycarbonyl), Teoc (2-(trimethylsilyl)ethoxycarbonyl) and Boc (t-butoxycarbonyl). In some embodiments, Prot is selected from Fmoc and Teoc.

In some embodiments, Prot is Fmoc.

In some embodiments, Prot is Teoc.

G

In some embodiments G¹ is

where m is from 0 to 6. In one embodiment, m is 5.

In some embodiments G¹ is

where p is from 0 to 30 and q is 0 or 1. In a preferred embodiment, q is 1 and p is 0 to 10, 1 to 8, preferably 4 to 8, most preferably 4 or 8.

In some embodiments, G² is

In some embodiments, G² is

In some embodiments, G² is

In some embodiments, G² is

where Hal is Cl, Br or I. In these embodiments, Hal may be preferably selected from Br and I. R^(B)

In some embodiments, R^(B) is boronic acid, i.e. —B(OH)₂.

In some embodiments, R^(B) is a boronate which may have the formula —B(OR)₂, where R is selected from C₁₋₄ alkyl, e.g. methyl, iso-propyl, or the formula —B(—O—R′—O—), where R′ is an C₂₋₁₀ alkylene group having between 2 and 4 carbon atoms in the chain between the oxygen atoms, e.g. —C₂H₄—, —C(CH₃)₂C(CH₃)₂—, —C₃H₆—.

In some embodiments, R^(B) is B⁻F₃K⁺.

In some embodiments, R^(B) is:

A particular preferred embodiment is compound 3.

1^(st) Aspect

In the first aspect of the present invention, the method of synthesis of a compound of formula I from a compound of formula III involves the removal of the SEM groups. In some embodiments, this may be achieved by the use of a reducing agent, such as super-hydride (lithium triethylborohydride), for example, in THF at a low temperature (e.g. −78° C.).

The treatment with the reducing agent may be followed by conventional work-up steps, such a dissolution in a mixture of solvents (e.g. methanol, dichloromethane and water) and treatment with silica gel to remove the SEM group.

3^(rd) Aspect

In the third aspect of the invention, the synthesis of a compound of formula IV from a compound of formula I involves the removal of the Prot group. Exemplary conditions for removal are set out in the table below.

Prot Exemplary removal conditions Fmoc (i) Amine base, such as piperidine (5%, 20%), morpholine (50%), dicyclohexamine (50%), p-dimethylaminopyridine (10%), diisopropylethylamine (50%) (ii) Bu₄NF in DMF Teoc (i) Bu₄NF, KF•2H₂O, CH₃CN, 50° C., 8 hours; (ii) ZnCl₂, CH₃NO₂ or ZnCl₂, CF₃CH₂OH; (iii) Tris(dimethylamino)sulfonium difluoromethylsilicate (TAS-F), DMF; (iv) Bu₄NCl, KF•2H₂O, CH₃CN, 45° C.; (v) CsF, DMF, t-BuOH, 90-110° C. Boc (i) Tosic Acid in tetrahydrofuran/dichloromethane (ii) 0.05M methanesulphonic acid in dioxane/dichloromethane (1:9) (iii) Ceric ammonium nitrate in acetonitrile (iv) ZnBr₂ in dichloromethane

The synthesis of a compound of formula V from a compound of formula I, involves the synthesis of a compound of formula IV as described above, followed by the addition of the group G to the compound of formula IV. This may be carried out using standard amide coupling conditions, using, for example, an amide coupling reagent, such as EDCI, HATU or HBTU, in a solvent such as DMF or DCM, and a reagent which is G-OH.

4^(th) aspect

In the fourth aspect of the present invention, where the synthesis of a compound of formula VIIa or VIIb from a compound of formula VI can be accomplished by coupling of a derivative of R² or R¹² respectively. The further synthesis of a compound of formula III from a compound of formula VIIa or VIIb can be accomplished by further coupling a derivative comprising R¹² or R² respectively.

Where the group being coupled is aromatic or olefinic, the derivative is an organometallic derivative, such as an organoboron derivative. The organoboron derivative may be a boronate or boronic acid.

Such couplings (Suzuki) are usually carried out in the presence of a palladium catalyst, for example Pd(PPh₃)₄, Pd(OCOCH₃)₂, PdCl₂, Pd₂(dba)₃. The coupling may be carried out under standard conditions, or may also be carried out under microwave conditions.

Where the group being coupled is an alkyne, the coupling method used is a Sonogashira coupling.

The Sonogashira coupling is carried out using two catalysts: a zerovalent palladium complex and a halide salt of copper(I). Phosphine-palladium complexes such as tetrakis(triphenylphosphine)palladium(0) are used for this reaction, but palladium(II) complexes can also be used because they are reduced to the palladium(0) species by the consumption of the terminal alkynes in the reaction medium. The oxidation of triphenylphosphine to triphenylphosphine oxide can also lead to the formation of Pd(0) in situ when catalysts such as bis(triphenylphosphine)palladium(II) chloride are used. In contrast, copper(I) halides react with the terminal alkyne and produce copper(I) acetylide, which acts as an activated species for the coupling reactions.

The reaction medium must be basic to neutralize the hydrogen halide produced as the byproduct of this coupling reaction, so alkylamine compounds such as triethylamine, diethylamine or piperidine are sometimes used as solvents, but also DMF or ether can be used as solvent. Other bases such as potassium carbonate or cesium carbonate are occasionally used.

The first coupling step is carried out with about a single equivalent (e.g. 0.9 or 1 to 1.1 or 1.2) of the derivative to be coupled, whereas the second coupling step may be carried out with more than a single equivalent of the derivative to be coupled acid.

The two coupling steps are usually carried out sequentially. They may be carried out with or without purification between the two steps. If no purification is carried out, then the two steps may be carried out in the same reaction vessel. Purification is usually required after the second coupling step. Purification of the compound from the undesired by-products may be carried out by column chromatography or ion-exchange separation.

The synthesis of compounds of formula IV are described in detail in WO 00/12508, which is incorporated herein by reference. In particular, reference is made to scheme 7 on page 24, where the desired compound is designated as intermediate P. This method is also disclosed in WO 2004/043963 and WO 2011/130616.

5^(th) Aspect

In the fifth aspect of the present invention, the synthesis of a compound of formula IXa from a compound of formula VIII can be accomplished by reaction with about a single equivalent (e.g. 0.9 or 1 to 1.1 or 1.2) of an appropriate alkene forming reagent, for example Wittig reagents (such as ylides), Tebbe reagents and Horner-Emmons-Wadworth reagents. Reference is made to the discussion on page 16 of WO 2010/043877, which is incorporated herein by reference. The synthesis of a compound of formula X from a compound of formula IXb may be accomplished using the same conditions, although greater than a single equivalent of the alkene forming reagent may be used.

The synthesis of a compound of formula X from a compound of formula IXa by an adaption of the methods described above for the synthesis of compounds of formula IV by triflation of the C2 keto group.

The synthesis of a compound of formula IXb from a compound of formula VIII by selective triflation using a single equivalent (e.g. 0.9 or 1 to 1.1 or 1.2) of the triflating agent.

In this aspect, synthesis via IXa may be preferred.

Synthesis of Compounds of Formula VI

The synthesis of compounds of formula VI are described in detail in WO 00/12508, which is incorporated herein by reference. In particular, reference is made to scheme 7 on page 24, where the above compound is designated as intermediate P. This method of synthesis is also described in WO 2004/043963.

EXAMPLES

General Experimental Methods

Optical rotations were measured on an ADP 220 polarimeter (Bellingham Stanley Ltd.) and concentrations (c) are given in g/100 mL. Melting points were measured using a digital melting point apparatus (Electrothermal). IR spectra were recorded on a Perkin-Elmer Spectrum 1000 FT IR Spectrometer. ¹H and ¹³C NMR spectra were acquired at 300 K using a Bruker Avance NMR spectrometer at 400 and 100 MHz, respectively. Chemical shifts are reported relative to TMS (δ=0.0 ppm), and signals are designated as s (singlet), d (doublet), t (triplet), dt (double triplet), dd (doublet of doublets), ddd (double doublet of doublets) or m (multiplet), with coupling constants given in Hertz (Hz). Mass spectroscopy (MS) data were collected using a Waters Micromass ZQ instrument coupled to a Waters 2695 HPLC with a Waters 2996 PDA. Waters Micromass ZQ parameters used were: Capillary (kV), 3.38; Cone (V), 35; Extractor (V), 3.0; Source temperature (° C.), 100; Desolvation Temperature (° C.), 200; Cone flow rate (L/h), 50; De-solvation flow rate (L/h), 250. High-resolution mass spectroscopy (HRMS) data were recorded on a Waters Micromass QTOF Global in positive W-mode using metal-coated borosilicate glass tips to introduce the samples into the instrument. Thin Layer Chromatography (TLC) was performed on silica gel aluminium plates (Merck 60, F₂₅₄), and flash chromatography utilised silica gel (Merck 60, 230-400 mesh ASTM). Except for the HOBt (NovaBiochem) and solid-supported reagents (Argonaut), all other chemicals and solvents were purchased from Sigma-Aldrich and were used as supplied without further purification. Anhydrous solvents were prepared by distillation under a dry nitrogen atmosphere in the presence of an appropriate drying agent, and were stored over 4 Å molecular sieves or sodium wire. Petroleum ether refers to the fraction boiling at 40-60° C.

General LC/MS Conditions:

Method 1 (default method, used unless stated otherwise)

The HPLC (Waters Alliance 2695) was run using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%). Gradient: initial composition 5% B held over 1.0 min, then increase from 5% B to 95% B over a 3 min period. The composition was held for 0.1 min at 95% B, then returned to 5% B in 0.03 minutes and hold there for 0.87 min. Total gradient run time equals 5 minutes.

Method 2

The HPLC (Waters Alliance 2695) was run using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%). Gradient: initial composition 5% B held over 1.0 minute, then increase from 5% B to 95% B over a 2.5 minute period. The composition was held for 0.5 minutes at 95% B, then returned to 5% B in 0.1 minutes and hold there for 0.9 min. Total gradient run time equals 5 minutes.

For Both Methods

Flow rate 3.0 mL/min, 400 μL was split via a zero dead volume tee piece which passes into the mass spectrometer. Wavelength detection range: 220 to 400 nm. Function type: diode array (535 scans). Column: Phenomenex Onyx Monolithic C18 50×4.60 mm.

Method 3

LC/MS (Shimazu LCMS-2020) using a mobile phase of water (A) (formic acid 0.1%) and acetonitrile (B) (formic acid 0.1%).

Gradient: initial composition 5% B held over 0.25 min, then increase from 5% B to 100% B over a 2 min period. The composition was held for 0.50 min at 100% B, then returned to 5% B in 0.05 minutes and hold there for 0.05 min. Total gradient run time equals 3 min. Flow rate 0.8 mL/min. Wavelength detection range: 190 to 800 nm. Oven temperature: 50° C. Column: Waters Acquity UPLC BEH Shield RP18 1.7 μm 2.1×50 mm.

Preparative HPLC:

Method 1 (Default, Unless Otherwise Specified)

The reverse phase flash purification conditions were as follows: The Flash purification system (Varian 971-Fp) was run using a mobile phase of water (A) and acetonitrile (B). Gradient: initial composition 5% B over 20 C.V. (Column Volume) then 5% B to 70% B within 60 C.V. The composition was held for 15 C.V. at 95% B, and then returned to 5% B in 5 C.V. and held at 5% B for 10 C.V. Total gradient run time equals 120 C.V. Flow rate 6.0 mL/min. Wavelength detection range: 254 nm. Column: Agilent AX1372-1 SF10-5.5 gC8.

Method 2

HPLC (Shimadzu UFLC) was run using a mobile phase of water (0.1% formic acid) A and acetonitrile (0.1% formic acid) B. Wavelength detection range: 254 nm. Column: Phenomenex Gemini 5μ C18 150×21-20 mm. Gradient:

B t = 0 13% t = 15.00 95% t = 17.00 95% t = 17.10 13% t = 20.00 13%

Total gradient run time is 20 min; flow rate 20.00 mL/min.

Example 1

(a) (R)-2-((R)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-methylbutanamido) propanoic acid (2)

HO-Ala-Val-H 1 (350 mg, 1.86 mmol) and Na₂CO₃ (493 mg, 4.65 mmol) were dissolved in distilled H₂O (15 mL) and the mixture was cooled to 0° C. before dioxane (15 mL) was added (partial precipitation of the amino acid salt occurred). A solution of Fmoc-CI (504 mg, 1.95 mmol) in dioxane (15 mL) was added dropwise with vigorous stirring over 10 minutes. The resulting mixture was stirred at 0° C. for 2 hours before the ice bath was removed and stirring was maintained for 16 hours. The solvent was removed by rotary evaporation under reduced pressure and the residue dissolved in water (150 mL). The pH was adjusted from 9 to 2 with 1N HCl and the aqueous layer was subsequently extracted with EtOAc (3×100 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure to afford pure HO-Ala-Val-Fmoc 2 (746 mg, 97% yield). LC/MS 2.85 min (ES+) m/z (relative intensity) 410.60; ¹H-NMR (400 MHz, CDCl₃) δ 7.79 (d, J=7.77 Hz, 2H), 7.60(d, J=7.77 Hz, 2H), 7.43(d, J=7.5 Hz, 2H), 7.34 (d, J=7.5 Hz, 2H), 6.30 (bs, 1H), 5.30 (bs, 1H), 4.71-7.56 (m, 1H), 4.54-4.36 (m, 2H), 4.08-3.91 (m, 1H), 2.21-2.07 (m, 1H), 1.50 (d, J=7.1 Hz, 3H), 1.06-0.90 (m, 6H).

(b) (9H-fluoren-9-yl)methyl((S)-3-methyl-1-oxo-1-(((S)-1-oxo-1-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)amino)propan-2-yl)amino)butan-2-yl)carbamate (3)

4-Aminophenylboronic acid pinacol ester was added (146.9 mg, 0.67 mmol) was added to a solution of HO-Ala-Val-Fmoc 2 (330 mg, 0.8 mmol), DCC (166 mg, 0.8 mmol) and DMAP (5 mg, cat.) in dry DCM (8 mL) previously stirred for 30 minutes at room temperature in a flask flushed with argon. The reaction mixture was then allowed to stir at room temperature overnight. The reaction was followed by LCMS and TLC. The reaction mixture was diluted with CH₂Cl₂ and the organics were washed with H₂O and brine before being dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dryloaded on a silicagel chromatography column (Hexane/EtOAc, 6:4) and pure product 3 was isolated as a white solid in 88% yield (360 mg).

Alternative Synthesis of 3

4-Aminophenylboronic acid pinacol ester was added (444 mg, 2.02 mmol) was added to a solution of HO-Ala-Val-Fmoc 2 (1 g, 2.43 mmol) and EEDQ (600 mg, 2.43 mmol) in dry DCM (20 mL) at room temperature in a flask flushed with argon. The reaction mixture was then allowed to stir at room temperature for 3.5 hours (or until complete). The reaction was followed by LCMS and TLC. The reaction mixture was diluted with CH₂Cl₂ and the organics were washed with H₂O and brine before being dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dryloaded on a silica gel chromatography column (Hexane/EtOAc, 6:4) and pure product 3 was isolated as a white solid in 58% yield (876 mg).

(c) 8-(3-((2-(4-((S)-2-((S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-methylbutanamido)propanamido)phenyl)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl trifluoromethanesulfonate (5)

1,1′-[[(Propane-1,3-diyl)dioxy]bis(11aS)-7-methoxy-2-[[(trifluoromethyl)sulfonyl]oxy]-10-((2-(trimethylsilyl)ethoxy)methyl)-1,10,11,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]-benzodiazepin-5,11-dione] 4 (2.03 g, 1.81 mmol), boronic pinacol ester (1 g, 1.63 mmol) and Na₂CO₃ (881 mg, 8.31 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (40 mL). The reaction flask was purged and filled with argon three times before tetrakis(triphenylphosphine)palladium(0) (41 mg, 0.035 mmol) was added and the reaction mixture heated to 30° C. overnight. The solvents were removed under reduce pressure and the residue was taken up in H₂O (100 mL) and extracted with EtOAc (3×100 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel chromatography column (Hexane/EtOAc, 8:2 to 25:75) to afford pure 5 in 33% yield (885 mg). LC/MS 3.85 min (ES+) m/z (relative intensity) 1452.90; ¹H NMR (400 MHz, CDCl₃) δ 7.78-7.16 (m, 17H), 7.13 (s, 1H), 6.51-6.24 (m, 1H), 5.51 (dd, J=10.0, 5.1 Hz, 2H), 5.36-5.11 (m, 1H), 4.74 (dd, J=10.1, 4.4 Hz, 2H), 4.70-4.53 (m, 2H), 4.47 (d, J=6.4 Hz, 1H), 4.37 (d, J=7.2 Hz, 1H), 4.27 (m, 4H), 4.20-4.14 (m, 1H), 3.90 (s, 3H), 3.89 (s, 3H), 3.77 (ddd, J=16.7, 9.0, 6.4 Hz, 3H), 3.71-3.61 (m, 2H), 3.24-2.91 (m, 3H), 2.55-2.33 (m, 2H), 2.22-2.07 (m, 1H), 1.52-1.37 (m, 3H), 1.04-0.86 (m, 10H), 0.00 (s, 18H).

(d) (9H-fluoren-9-yl)methyl((2S)-1-(((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (6)

Triphenylarsine (42 mg, 0.137 mmol) was added to a mixture of PBD-triflate 5 (250 mg, 0.172 mmol), cyclopropylboronic acid (73.9 mg, 0.86 mmol), silver oxide (159 mg, 0.688 mmol) and potassium phosphate tribasic (438 mg, 2.06 mmol) in dry dioxane (10 mL) under an argon atmosphere. The reaction was flushed with argon 3 times and bis(benzonitrile)palladium(II) chloride (13.2 mg, 0.034 mmol) was added. The reaction was flushed with Argon 3 more times before being warmed to 75° C. and stirred for 10 minutes. The reaction mixture was filtered through a pad of celite which was subsequently rinsed with ethyl acetate. The solvent was removed by rotary evaporation under reduced pressure. The resulting residue was subjected to flash column chromatography (silica gel; 1% methanol/chloroform). Pure fractions were collected and combined, and excess eluent was removed by rotary evaporation under reduced pressure to afford the desired product 6 (132 mg, 50% yield). LC/MS 3.83 min (ES+) m/z (relative intensity) 1345.91; ¹H NMR (400 MHz, CDCl₃) δ 7.88-7.14 (m, 17H), 6.69 (s, 1H), 6.45-6.25 (m, 1H), 5.57-5.41 (m, 2H), 5.34-5.14 (m, 1H), 4.78-4.67 (m, 2H), 4.62-4.55 (m, 1H), 4.50-4.45 (m, 2H), 4.51-4.44 (m, 1H), 4.31-4.21 (m, 4H), 4.16 (m, 1H), 3.92 (s, 3H), 3.86 (s, 3H), 3.82-3.71 (m, 2H), 3.66 (m, 3H), 3.40-3.28 (m, 1H), 3.07 (m, 1H), 2.70-2.57 (m, 1H), 2.47-2.36 (m, 2H), 2.15 (m, 1H), 1.51-1.40 (m, 3H), 1.03-0.87 (m, 11H), 0.77-0.71 (m, 2H), 0.60-0.54 (m, 2H), 0.00 (t, J=3.0 Hz, 18H).

(e) (9H-fluoren-9-yl)methyl((2S)-1-(((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1 H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (7)

A solution of Super-Hydride® (0.5 mL, 1M in THF) was added dropwise to a solution of SEM dilactam 6 (265 mg g, 0.19 mmol) in THF (10 mL) at −78° C. under an argon atmosphere. The addition was completed over 5 minutes in order to maintain the internal temperature of the reaction mixture constant. After 20 minutes, an aliquot was quenched with water for LC/MS analysis, which revealed that the reaction was complete. Water (20 mL) was added to the reaction mixture and the cold bath was removed. The organic layer was extracted with EtOAc (3×30 mL) and the combined organics were washed with brine (50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dissolved in MeOH (12 mL), CH₂Cl₂ (6 mL), water (2 mL) and enough silica gel to form a thick stirring suspension. After 5 days, the suspension was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (200 mL) until the elution of the product was complete. The organic layer was washed with brine (2×70 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. Purification by silica gel column chromatography (100% CHCl₃ to 96% CHCl₃/4% MeOH) afforded the product 7 as a yellow solid (162 mg, 78%). LC/MS 3.02 min (ES+) m/z (relative intensity) 1052.37.

(f) (2S)-2-amino-N-((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (8)

Excess piperidine was added (0.2 mL, 2 mmol) to a solution of SEM-dilactam 7 (76 mg, 0.073 mmol) in DMF (1 mL). The mixture was allowed to stir at room temperature for 20 min, at which point the reaction had gone to completion (as monitored by LC/MS). The reaction mixture was diluted with CH₂Cl₂ (75 mL) and the organic phase was washed with H₂O (3×75 mL) until complete piperidine removal. The organic phase was dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure to afford crude product 8 which was used as such in the next step. LC/MS 2.32 min (ES+) m/z (relative intensity) 830.00.

(g) N-((2S)-1-(((2S)-1-((4-(8-(3-((2-cyclopropyl-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)-1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3,6,9,12,15,18,21,24-octaoxaheptacosan-27-amide (9)

EDCI hydrochloride (14 mg, 0.0732 mmol) was added to a suspension of Maleimide-PEG₈-acid (43.4 mg, 0.0732 mmol) in dry CH₂Cl₂ (5 mL) under argon atmosphere. The mixture was stirred for 1 hour at room temperature before PBD 8 (60.7 mg, 0.0732 mmol) was added. Stirring was maintained until the reaction was complete (usually 5 hours). The reaction was diluted with CH₂Cl₂ and the organic phase was washed with H₂O and brine before being dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure by rotary evaporation under reduced pressure. The product was purified by careful silica gel chromatography (slow elution starting with 100% CHCl₃ up to 9:1 CHCl₃/MeOH) followed by reverse phase chromatography to remove unreacted maleimide-PEG₈-acid. The product 9 was isolated in 17.6% (21.8 mg). LC/MS 2.57 min (ES+) m/z (relative intensity) 1405.30; ¹H NMR (400 MHz, CDCl₃) δ 7.91 (t, J=3.5 Hz, 1H), 7.80 (d, J=4.0 Hz, 1H), 7.75 (d, J=8.8 Hz, 1H), 7.69 (d, J=8.7 Hz, 1H), 7.54-7.50 (m, 2H), 7.45 (s, 1H), 7.39-7.31 (m, 2H), 6.87 (d, J=10.5 Hz, 2H), 6.76 (s, 1H), 6.72-6.68 (m, 2H), 4.74-4.62 (m, 1H), 4.45-4.17 (m, 7H), 3.95 (s, 3H), 3.94 (s, 3H), 3.67-3.58 (m, 34H), 3.54 (m, 2H), 3.42 (dd, J=10.2, 5.2 Hz, 2H), 3.16-3.07 (m, 1H), 2.92 (dd, J=16.1, 4.1 Hz, 1H), 2.62-2.49 (m, 4H), 2.48-2.39 (m, 2H), 2.37-2.25 (m, 1H), 1.92 (s, 1H), 1.52-1.44 (m, 3H), 1.10-0.93 (m, 6H), 0.79 (dd, J=9.2, 5.3 Hz, 2H), 0.57 (dd, J=9.2, 5.3 Hz, 2H), NH were not observed.

Example 2

(a) (S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl trifluoromethanesulfonate (10)

Pd(PPh₃)₄ (20.6 mg, 0.018 mmol) was added to a stirred mixture of the bis-enol triflate 4 (500 mg, 0.44 mmol), N-methyl piperazine boronic ester (100 mg, 0.4 mmol), Na₂CO₃ (218 mg, 2.05 mmol), MeOH (2.5 mL), toluene (5 mL) and water (2.5 mL). The reaction mixture was allowed to stir at 30° C. under a nitrogen atmosphere for 24 hours after which time all the boronic ester has consumed. The reaction mixture was then evaporated to dryness before the residue was taken up in EtOAc (100 mL) and washed with H₂O (2×50 mL), brine (50 mL), dried (MgSO₄), filtered and evaporated under reduced pressure to provide the crude product. Purification by flash chromatography (gradient elution: 80:20 v/v Hexane/EtOAc to 60:40 v/v Hexane/EtOAc) afforded product 10 as a yellowish foam (122.6 mg, 25%). LC/MS 3.15 min (ES+) m/z (relative intensity) 1144 ([M+H]⁺; 20%).

(b) (9H-fluoren-9-yl)methyl((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (11)

PBD-triflate 10 (359 mg, 0.314 mmol), boronic pinacol ester 3 (250 mg, 0.408 mmol) and triethylamine (0.35 mL, 2.51 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (3 mL). The microwave vessel was purged and filled with argon three times before tetrakis(triphenylphosphine)palladium(0) (21.7 mg, 0.018 mmol) was added and the reaction mixture placed in the microwave at 80° C. for 10 minutes. Subsequently, CH₂Cl₂ (100 mL) was added and the organics were washed with water (2×50 mL) and brine (50 mL) before being dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel chromatography column (CHCl₃/MeOH, 100% to 9:1) to afford pure 11 (200 mg, 43% yield). LC/MS 3.27 min (ES+) m/z (relative intensity) 1478 ([M+H]⁺; 100%).

(c) (9H-fluoren-9-yl)methyl((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (12)

A solution of Super-Hydride® (0.34 mL, 1M in THF) was added dropwise to a solution of SEM-dilactam 11 (200 mg, 0.135 mmol) in THF (5 mL) at −78° C. under an argon atmosphere. The addition was completed over 5 minutes in order to maintain the internal temperature of the reaction mixture constant. After 20 minutes, an aliquot was quenched with water for LC/MS analysis, which revealed that the reaction was complete. Water (20 mL) was added to the reaction mixture and the cold bath was removed. The organic layer was extracted with EtOAc (3×30 mL) and the combined organics were washed with brine (50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. The crude product was dissolved in MeOH (6 mL), CH₂Cl₂ (3 mL), water (1 mL) and enough silica gel to form a thick stirring suspension. After 5 days, the suspension was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (100 mL) until the elution of the product was complete. The organic layer was washed with brine (2×50 mL), dried with MgSO₄, filtered and the solvent removed by rotary evaporation under reduced pressure. Purification by silica gel column chromatography (100% CHCl₃ to 96% CHCl₃/4% MeOH) afforded the product 12 as a yellow solid (100 mg, 63%). LC/MS 2.67 min (ES+) m/z (relative intensity) 1186 ([M+H]⁺; 5%).

(d) (S)-2-amino-N—((S)-1-((4-((R)-7-methoxy-8-(3-(((R)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (13)

Excess piperidine was added (0.1 mL, 1 mmol) to a solution of PBD 12 (36.4 mg, 0.03 mmol) in DMF (0.9 mL). The mixture was allowed to stir at room temperature for 20 min, at which point the reaction had gone to completion (as monitored by LC/MS). The reaction mixture was diluted with CH₂Cl₂ (50 mL) and the organic phase was washed with H₂O (3×50 mL) until complete piperidine removal. The organic phase was dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure to afford crude product 13 which was used as such in the next step. LC/MS 2.20 min (ES+) m/z (relative intensity) 964 ([M+H]⁺; 5%).

(e) 6-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-N—((S)-1-(((S)-1-((4-((S)-7-methoxy-8-(3-(((S)-7-methoxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)hexanamide (14)

EDCI hydrochloride (4.7 mg, 0.03 mmol) was added to a suspension of 6-maleimidohexanoic acid (6.5 mg, 0.03 mmol) in dry CH₂Cl₂ (3 mL) under argon atmosphere. The mixture was stirred for 1 hour at room temperature before PBD 13 (34 mg, crude) was added. Stirring was maintained until the reaction was complete (6 hours). The reaction was diluted with CH₂Cl₂ and the organic phase was washed with H₂O and brine before being dried over MgSO₄, filtered and excess solvent removed by rotary evaporation under reduced pressure by rotary evaporation under reduced pressure. The product was purified by careful silica gel chromatography (slow elution starting with 100% CHCl₃ up to 9:1 CHCl₃/MeOH) followed by reverse phase chromatography to remove unreacted maleimide-PEG₈-acid. The product 14 was isolated in 41% over two steps (14.6 mg). LC/MS 2.40 min (ES+) m/z (relative intensity) 1157 ([M+H]⁺5%)

Example 3 Alternative Synthesis of Compound 11

PBD-triflate 5 (469 mg, 0.323 mmol), boronic pinacol ester (146.5 mg, 0.484 mmol) and Na₂CO₃ (157 mg, 1.48 mmol) were dissolved in a mixture of toluene/MeOH/H₂O, 2:1:1 (10 mL). The reaction flask was purged with argon three times before tetrakis(triphenylphosphine)palladium(0) (7.41 mg, 0.0064 mmol) was added and the reaction mixture heated to 30° C. overnight. The solvents were removed under reduced pressure and the residue was taken up in H₂O (50 mL) and extracted with EtOAc (3×50 mL). The combined organics were washed with brine (100 mL), dried with MgSO₄, filtered and the volatiles removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel column chromatography (CHCl₃ 100% to CHCl₃/MeOH 95%:5%) to afford pure 11 in 33% yield (885 mg). LC/MS 3.27 min (ES+) m/z (relative intensity) 1478 ([M+H]⁺; 100%).

Example 4

(a) 9H-Fluoren-9-yl)methyl((S)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (15)

The triflate 5 (0.5 g, 0.35 mmol, 1 equiv.), 3,4-(methylenedioxy)phenyl boronic acid (75 mg, 0.45 mmol, 1.3 equiv.) and Na₂CO₃ (0.17 g, 1.6 mmol, 4.5 equiv.) were dissolved in toluene (11 mL), EtOH (5.5 mL) and water (5.5 mL) under an Ar atmosphere. The flask was evacuated and flushed with Ar three times. Pd(PPh₃)₄ (24 mg, 0.02 mmol, 0.06 equiv.) was added and again the flask was evacuated and flushed with Ar three times. This was heated to 30° C. and left stirring overnight. Analysis by LC/MS showed complete loss of starting material. The solvent was removed in vacuo and the residue dissolved in water (60 mL) before washing with ethyl acetate (60 mL×3). The combined organic layers were washed with brine (50 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by column chromatography (50:50 to 25:75 v/v hexane/ethyl acetate) afforded the product 15 as a yellow solid (310 mg, 64%). LC/MS (method 3)(1.44 min (ES⁻) m/z (relative intensity) 1423.35 ([M−H]⁻; 79).

(b) (9H-Fluoren-9-yl)methyl((S)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)carbamate (16)

SEM dilactam 15 (0.31 g, 0.22 mmol, 1 equiv.) was dissolved in THF (10 mL) and cooled to −78° C. under an Ar atmosphere. Super-Hydride® (0.5 mL, 1 M in THF, 2.5 equiv.) was added drop wise over 5 minutes while monitoring the temperature. After 30 minutes a small sample was taken and worked-up for LC/MS analysis. Water (50 mL) was added, the cold bath was removed and the solution washed with ethyl acetate (50 mL). The organic layer was extracted and washed with brine (60 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. The crude product was dissolved in EtOH (13.2 mL), CH₂Cl₂ (6.6 mL) and water (2.2 mL) and enough silica gel was added until it was a thick suspension. After 5 days stirring, it was filtered through a sintered funnel and washed with CH₂Cl₂/MeOH (9:1) (100 mL) until product ceased to be eluted. The organic layer was washed with brine (2×50 mL), dried with MgSO₄, filtered and the solvent removed in vacuo. Purification by silica gel column chromatography (CHCl₃ with 1% to 4% MeOH gradient) afforded the pure product 16 as a yellow solid (185 mg, 75%). LC/MS (method 3) (1.70 min (ES⁺) m/z (relative intensity) 1132.85 ([M+H]⁺; 60).

(c) (S)-2-Amino-N—((S)-1-((4-((S)-8-(3-(((S)-2-(benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)-3-methylbutanamide (17)

The imine 16 (82 mg, 0.07 mmol, 1 equiv.) was dissolved in DMF (1 mL) before piperidine (0.2 mL, 2 mmol, excess) was added slowly. This solution was left to stir at room temperature for 20 minutes until LC/MS analysis showed complete consumption of starting material. The reaction mixture was diluted with CH₂Cl₂ (50 mL), washed with water (50 mL×4), dried with MgSO₄, filtered and the solvent removed in vacuo. The product 17 was used without further purification in the next step. LC/MS (method 3) (1.15 min (ES⁺) m/z (relative intensity) 910.60 ([M+H]⁺; 58).

(D) N—((S)-1-(((S)-1-((4-((S)-8-(3-(((S)-2-(Benzo[d][1,3]dioxol-5-yl)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yl)oxy)propoxy)-7-methoxy-5-oxo-5,11a-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-2-yl)phenyl)amino)-1-oxopropan-2-yl)amino)-3-methyl-1-oxobutan-2-yl)-1-(3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanamido)-3,6,9,12,15,18,21,24-octaoxaheptacosan-27-amide (18)

The imine 17 (92 mg, 0.1 mmol, 1.1 equiv.) was dissolved in CHCl₃ (6 mL) with one drop of anhydrous MeOH to aid dissolution. Maleimide-PEG₈-acid (53 mg, 0.09 mmol, 1 equiv.) was added followed by EEDQ (33 mg, 0.14 mmol, 1.5 equiv.). This was left to stir vigorously at room temperature under Ar for 4 days until LC/MS analysis showed majority product formation. The solvent was removed in vacuo and the crude product was partially purified by silica gel column chromatography (CHCl3 with 1% to 10% MeOH gradient) yielding 18 (81 mg). The material was purified further by preparative HPLC (method 2) to give 18 as a yellow solid (26.3 mg, 18%). Fast Formic run: LC/MS (method 3)(1.39 min (ES+) m/z (relative intensity) 1485.00 ([M+H]+., 64).

Abbreviations

-   Ac acetyl -   Acm acetamidomethyl -   Alloc allyloxycarbonyl -   Boc di-tert-butyl dicarbonate -   t-Bu tert-butyl -   Bzl benzyl, where Bzl-OMe is methoxybenzyl and Bzl-Me is     methylbenzene -   Cbz or Z benzyloxy-carbonyl, where Z—CI and Z—Br are chloro- and     bromobenzyloxy carbonyl respectively -   DMF N,N-dimethylformamide -   Dnp dinitrophenyl -   DTT dithiothreitol -   Fmoc 9H-fluoren-9-ylmethoxycarbonyl -   imp N-10 imine protecting group:     3-(2-methoxyethoxyl)propanoate-Val-Ala-PAB -   MC-OSu maleimidocaproyl-O—N-succinimide -   Moc methoxycarbonyl -   MP maleimidopropanamide -   Mtr 4-methoxy-2,3,6-trimethtylbenzenesulfonyl -   PAB para-aminobenzyloxycarbonyl -   PEG ethyleneoxy -   PNZ p-nitrobenzyl carbamate -   Psec 2-(phenylsulfonyl)ethoxycarbonyl -   TBDMS tert-butyldimethylsilyl -   TBDPS tert-butyldiphenylsilyl -   Teoc 2-(trimethylsilyl)ethoxycarbonyl -   Tos tosyl -   Troc 2,2,2-trichlorethoxycarbonyl chloride -   Trt trityl -   Xan xanthyl 

The invention claimed is:
 1. A method of synthesizing a compound of formula III:,

from a compound of formula VI:

which proceeds via a compound of formula VIIa or VI lb:

wherein: R² is selected from a group of: (a) formula IIa:

where A is a phenyl or C₅₋₇ heteroaryl group, and either: (i) Q¹ is a single bond, and Q² is selected from a single bond and —Z—(CH₂)_(n)—, where Z is selected from a single bond, O, S and NH and n is from 1 to 3, or (ii) Q¹ is —CH═CH—, and Q² is a single bond; (b) formula IIb:

R^(C1), R^(C2) and R^(C3) are independently selected from H and unsubstituted C₁₋₂ alkyl; (c) formula IIc:

L² is selected from a single bond and a group of: (a)

wherein n is 0 to 3; (b)

 wherein n is as defined above; (c)

 wherein n is as defined above; and (d)

 wherein n is as defined above, E is O, S or NR, D is N, CH, or CR, and F is N, CH, or CR; L¹ is:

 where X is such that L¹ is an amino-acid residue, a dipeptide residue or a tripeptide residue; Prot is selected from Fmoc (fluorenylmethyloxycarbonyl), Teoc (2-(trimethylsilyl)ethoxycarbonyl) and Boc (t-butoxycarbonyl); R¹² is selected from: (a) C₅₋₁₀ heteroaryl, phenyl, or naphthyl group, optionally substituted by one or more substituents selected from the group consisting of: halo, nitro, cyano, C₁₋₇ alkoxy, C₃₋₂₀ heterocyclyloxy, phenoxy, naphthyloxy, C₅₋₂₀ heteroaryloxy, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (b) C₁₋₅ saturated aliphatic alkyl; (c) C₃₋₆ saturated cycloalkyl; (d)

 wherein each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5; (e)

 wherein one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and (f)

 where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; R⁶, R^(6 ′), R⁹ and R^(9′) are H; R⁷ is C₁₋₇, alkoxy; R″ is a C₃₋₁₂ alkylene group, which chain may be interrupted by one or more heteroatoms selected from O, S, NR^(N2) (where R^(N2) is H or C₁₋₄ alkyl), and/or aromatic rings selected from benzene and pyridine; Y and Y′ are selected from O, S, and NH; SEM is 2-((trimethylsilyl)ethoxy)methyl; OTf is CF₃SO₃; C₃₋₂₀ heterocyclyl is a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound, which moiety has from 3 to 20 ring atoms, of which from 1 to 10 are ring heteroatoms selected from O, S, and N; C₃₋₇ heterocyclyl is a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound, which moiety has from 3 to 7 ring atoms, of which from 1 to 4 are ring heteroatoms selected from O, S, and N; C₅₋₂₀ heteroaryl is a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of a heteroaromatic compound, which moiety has from 5 to 20 ring atoms, of which from 1 to 10 are ring heteroatoms selected from O, S, and N; C₅₋₁₀ heteroaryl is a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of a heteroaromatic compound, which moiety has from 5 to 10 ring atoms, of which from 1 to 4 are ring heteroatoms selected from O, S, and N; C₅₋₇ heteroaryl is a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of a heteroaromatic compound, which moiety has from 5 to 20 ring atoms, of which from 1 to 4 are ring heteroatoms selected from O, S, and N; and R^(7′) is selected from the same groups as R⁷; wherein the R² group is introduced by coupling a compound of formula XIa, XIb or XIc:

(a)

(b)

(c) wherein the R¹² group is introduced by coupling a derivative comprising R¹² which, when R¹² is

 is

 or otherwise the derivative is R^(B′) —R¹², where R^(B) represents boronic acid or a boronate and R^(B′) represents boronic acid or a boronate.
 2. The method according to claim 1, wherein Y and Y′ are O and R″ is a C₃₋₇ alkylene group with no substituents.
 3. The method according to claim 2, wherein R″ is a C₃, C₅ or C₇ alkylene group.
 4. The method according to claim 1, wherein R⁷ is methoxy.
 5. The method according to claim 1, wherein R¹² is selected from: (a) phenyl; (b) methyl, ethyl or propyl; (c)

(d)

 wherein one of R^(25a) and R^(25b) is H and the other is phenyl; and (e)

 wherein R²⁴ is selected from H and methyl.
 6. The method according to claims 1, wherein R² is a group of formula IIa, and Q¹ is a single bond.
 7. The method according to claim 6, wherein Q² is a single bond.
 8. The method according to claim 6, wherein Q² is a —Z—(CH₂)_(n)—, Z is selected from 0 and S, and n is selected from 1 or
 2. 9. The method according to claim 1, wherein R² is selected from: (a) a group of formula IIa, and Q¹ is —CH═CH—; (b) a group of formula IIb, and R^(C1), R^(C2) and R^(C3) are all H; (c) a group of formula IIb, and R^(C1), R^(C2) and R^(C3) are all methyl; and (d) a group of formula IIb, and R^(C1), R^(C2) and R^(C3) are independently selected from H and methyl.
 10. The method according to claim 1, wherein L² is a single bond.
 11. The method according to claim 1, wherein L² is selected from: (a)

 and n is 0 or 1; (b)

 and n is 0 or 1; (c)

 and n is 0 or 1; (d)

 and n is 0 or
 1. 12. The method according to any claim 1, wherein L¹ comprises a dipeptide residue.
 13. The method according to claim 12, wherein L¹ is selected from: ^(Prot)-Phe-Lys-^(L2), ^(Prot)-Val-Ala-^(L2), ^(Prot)-Val-LyS-^(L2), ^(Prot)-Ala-Lys-^(L2), ^(Prot)-Val-Cit-^(L2), ^(Prot)-Phe-Cit-^(L2), ^(Prot)-Leu-Cit-^(L2), ^(Prot)-Ile-Cit-^(L2), ^(Prot)-Phe-Arg-^(L2), and ^(Prot)-Trp-Cit-^(L2).
 14. The method according to claim 13, wherein L¹ is selected from: ^(Prot)-Phe-Lys-^(L2), ^(Prot)-Val-Ala- ^(L2), ^(Prot)-Val-Lys- ^(L2), ^(Prot)-Ala-Lys- ^(L2), and ^(Prot)-Val-Cit- ^(L2).
 15. The method according to claim 14, wherein L¹ is selected from ^(Prot)-Phe-Lys-^(L2), ^(Prot)-Val-Cit-^(L2) or ^(Prot)-Val-Ala-^(L2).
 16. The method according to claim 1, wherein Prot is Fmoc or Teoc.
 17. The method according to claim 1, wherein R^(B) is selected from: (a) —B(OH)₂; (b) —B(OR)₂, where R is selected from C₁₋₄ alkyl; (c) —B(—O—R′—O—), where R′ is an C₂₋₁₀ alkylene group having between 2 and 4 carbon atoms in the chain between the oxygen atoms; (d) B⁻F₃K⁺; and (e) 